This invention is directed to a hollow fiber membrane contactor.
Hollow fiber membrane contactors are known. For example, see U.S. Pat. Nos. 3,288,877; 3,755,034; 4,220,535; 4,664,681; 4,940,617; 5,186,832; 5,264,171; 5,284,584; and 5,449,457, each is incorporated herein by reference. In general, such contactors utilize a thin walled membrane to separate, via diffusion, gaseous, solid or liquid components from a solution or colloidal mixture. Hollow fiber membrane diffusion contactors are commercially available under the name of LIQUI-CEL(copyright) from Celgard, Inc. of Charlotte, N.C. and under the name of SEPAREL(copyright) from Dianippon Ink and Chemicals of Tokyo, Japan (DIC). Such contactors have numerous uses, one being the degassing of fluids.
The SEPAREL(copyright) contactor comprises a shell surrounding a hollow fiber fabric that is wound around a perforated core. The SEPAREL(copyright) contactor uses a fabric made of polymethyl pentene (PMP) hollow fibers and polyester yarn. Hollow fibers made from PMP exhibits unique diffusion properties. See Japanese Kokai 2-102714 (published Apr. 16, 1990). Additionally, the SEPAREL(copyright) contactor operating parameters are limited to a maximum temperature of 50xc2x0 C. and a maximum feed water pressure of 0.4 Mpa. See, Hollow Fiber Membrane Degassing Modulexe2x80x94SEPAREL(copyright), www.dic.co.jp.
Commercial PMP fabrics used in the manufacture of contactors utilize the PMP hollow fibers as the fill or weft and polyester yarns as the warp yarn. This fabric has a tendency to break if the fabric is wound under tension. One possible explanation for this weakness is the use of polyester warp yarn in the production of the fabric. Polyester is a relatively stiff material that does not bend and flex well. When a PMP fabric is wound around a mandrel the warp yarns absorb most of the applied load, thus fabrics using polyester warp yarns break and tear. Fabrics similar to those described in Japanese Kokai 2-102714 have been shown to break at essentially zero tension during winding. Some degree of winding tension is desirable to create a well-formed fiber bundle that fits properly within a contactor shell.
Another possible explanation for the tearing exhibited by such PMP fabrics is a failure to utilize properly spaced or sized warp yarn. For example, fabrics similar to those described in Japanese Kokai 2-102714 (which tear during winding) exhibit a maximum warp yarn count of approximately 5 lines (yarns) per inch. See JP 2-102714, Embodiment 3.
U.S. Pat. No. 4,911,846 discloses an artificial lung made with a hollow fiber cord fabric. Note, U.S. Pat. No. 4,911,846, FIGS. 11 and 12. The cord fabric comprises polyolefin hollow fibers (including PMP hollow fibers), as weft fibers and warp fibers (including polyesters, polyamides, polyimides, polyacrylonitriles, polypropylenes, polyarylates, polyvinyl alcohols, etc.). The warp yarns are preferably multifilament yarns of polyesters or polyamides having a yarn fineness of 10 to 150 deniers, more preferably 25 to 75 deniers. See U.S. Pat. No. 4,911,846 col. 6, lines 3-14. No information is provided regarding the spacing of the warp yarn or the makeup of non-polyester, non-polyamide warp yarns.
Accordingly, a need exists for an improved contactor preferably employing a fabric that is not susceptible to breakage and operable at higher temperatures and pressures than known PMP hollow fiber contactors.
The present invention is directed to a contactor for degassing a liquid comprising a perforated core and a microporous membrane fabric wrapped around the core. The fabric comprises a polymethyl pentene hollow fiber, as a weft fiber, and a polyolefin warp yarn. In preferred embodiments the fabric has a weft fiber count between 50 and 70 fibers per inch and a warp yarn count between 3 and 12 yarns per inch. A tube sheet secures the ends of the wound fabric and a shell encases the tube sheet and wound fabric. The shell has at least one opening to permit liquid flow through the shell and an end cap.
In a further embodiment, the invention is directed to a contactor for degassing a liquid wherein the contactor is adapted to withstand pressures greater than 0.4 MPa and temperatures greater than 50xc2x0 C. The contactor according to this embodiment further comprises a shell and a microporous membrane fabric comprising a polymethyl pentene hollow fiber, as a weft fiber, and a warp yarn with fiber and yarn counts similar to those mentioned above. The fabric is preferably wrapped around a perforated core and situated inside the shell. The shell has at least one opening to permit the liquid flow through the shell.